Abstract: Novel CO2 adsorbents were prepared by grafting of two different aminosilanes on mesoporous silica MCM-41 and SBA-15. The properties of the mesoporous materials before and after surface modification were investigated by powder X-ray diffraction (XRD) pattern, solid-state 29Si nuclear magnetic resonance (NMR), Fourier transforminfrared (FT-IR) spectra, and measurements of N2 adsorption and desorption isothermal, which confirmed that aminosilanes were grafted on the surface of the channels in the mesoporous materials. Thermogravimetry analysis (TGA) evaluated the amounts of grafted amine to be about 1.5-2.9 mmol·g-1. The CO2 adsorption capacities of MCM-41 increased from 0.67 mmol·g-1 to 2.20 mmol·g-1 after AEAPMDS (N-β-(aminoethyl)-γ-aminopropyl dimethoxy methylsilane) modification (p =101 kPa) at room temperature. The studies of the mechanism of CO2 adsorption suggested that there were two main contributions for the increase: the chemical adsorption based on the active sites of amine groups and the capillary condensation caused by the nano-scale channels of the mesoporous materials.